NEW YORK — The U.S. stock market blasted through another major milestone Friday, with the Standard & Poor's 500 stock index closing above 1800 for the first time, putting the benchmark index on track for its best annual gain in 15 years.

The S&P 500, which closed up 8.91 points, or 0.50%, to a record 1804.76, also posted its 37th record close this year, the most since it notched 47 new highs in 1998. Its year-to-date gain is now 26.54%, putting it within striking distance of its 26.67% gain in 1998.

The index, which is home to large companies that account for roughly 70% of the entire value of the U.S. stock market, has now topped 1600, 1700 and 1800 this year for the first time, after waiting more than 13 years to climb from 1500 to 1600.

The blue-chip Dow Jones industrial average, which closed above 16,000 for the first time on Thursday, continued its record-setting run Friday, too. It rose 54.78 points, or 0.34%, to 16,064.77. It was the Dow's 41st closing high of 2013.

The Nasdaq composite also hit a fresh 13-year high, rising 22.49 points, or 0.57%, to 3991.65. The tech-packed index is within striking distance of reclaiming the 4000 level, which it last saw back in 2000.

Surpassing big round numbers like Dow 16,000 and 1800 on the S&P 500 are bound to attract the attention of investors, says Jeff Kleintop, chief investment strategist at LPL Financial. "It is another flag that is waiving and screaming, 'you are missing out,'" he says.

The U.S. stock market has been propelled higher by a combination of solid corporate earnings, a steadily strengthening economy and the Federal Reserve's easy-money monetary policy. The Fed, which will be headed by new chief Janet Yellen starting in January when she replaces current chairman Ben Bernanke, is unlikely to start dialing back on its market-friendly bond-buying program until some time in the first quarter of 2014, analysts predict.

Despite some bears warning of an inflating stock market bubble, Kleintop says there are few traditional signs of a bubble and that the market is being supported by reasonable valuations and still-low interest rates.

He notes that the S&P 500 is currently trading around 16 times its earnings the past 12 months, which is a tad higher than the rough average of around 15, but still below the peak P-E ratio of 17 or 18 during past bull markets since World War II. He also says the economy, which is growing below 3%, is not strong enough to create bubble-like conditions. And the Fed, he adds, "will still be there to support the market next year."

But the market's sharp rise in 2013 has some Wall Street pros a little squeamish, at least in the short-term.

Gary Flam, portfolio manager at Bel Air Investment Advisors, says he is "cautions" in the near term. "We do not see current market levels as providing an advantageous risk-reward to add exposure to U.S. stocks," he says.

Flam says the leadership transition at the Fed next year could pose risks for the market, adding that fiscal headwinds also could be an obstacle. The fact that stocks are trading at average historical valuations, also could limit the market's upside, he adds.

"For further advances, we will need earnings growth," Flam says.

Kleintop says Wall Street will be closely watching retail sales on Black Friday to get a gauge on whether the consumer is still willing to spend despite a so-so economy and tough job market. "That's the next market catalyst," he says, adding that he thinks retail sales could surprise to the upside given a sharp drop in gas prices and from the fact that many consumers might feel more inclined to spend as the value of their stock portfolios rise.